Conventional tube lamps (fluorescent lamps) of the type having a two-pin connector at each end of the tube are, in steady-state operation, powered by a DC or AC electric current flowing between the connectors. The connectors are electrically disconnected until an arc has established in the tube. For this purpose, a starting procedure including preheating of the electrodes may be carried out by dedicated starting circuitry, which can be made inherently safe by being enabled only when the lamp is properly inserted into the fixture, so that live electric parts are always protected from touch. The starting circuitry may be of the switch-start/preheat, rapid-start or other type, and is commonly integrated in the lighting fixture.
It is desirable to power a tube lamp retrofit in the same manner as the tube lamp it replaces, that is, by a current flowing between its end connectors. Depending on the internal circuitry of the lamp, potentially hazardous conditions may arise when the lamp is partially inserted or partially removed from the fixture. CN 101737664 A proposes a lamp with a protection switch actuated by an external push button located next to a pair of external connection pins. When the push button is depressed, which normally occurs only at proper insertion of the connection pins into a socket, the protection switch connects one of the pins to the electrical components within the lamp. However, such external push button may be easily tampered with.